The Three-Dimensional Coordinate And Shape Fitting Algorithm of Steel Ring of Shield Tunnel Gate
In order to solve the problem of accurate and rapid measurement of steel ring of shield tunnel,an algorithm was introduced to obtain the position and attitude information of"three-dimensional coordinates,radius,roundness,flatness,verticality"of steel ring of tunnel door by fitting space circle according to the observation point.Based on the characteristics that the steel ring of the tunnel gate is a standard circle and the geometric relation that the vertical plane of the chord length of the space circle intersects the center of the circle,the algorithm formula of fitting the space circle with multiple observation points was derived.Through the theory of"least square method"and"adjustment model with restriction conditions",the formula equations were linearized and combined to form matrix equations.By using computer programming,the form of matrix equation was specified,and the calculation steps such as"string length combination method","plane fitting method","confluence of constraints"and"least squares solution form"were introduced.The reliability of the proposed algorithm was verified by comparing the calculation results of commercial tunnel measurement software with the installation case of tunnel door steel ring in a subway project.
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